We have a good understanding of how to downgrade and what works on older Macs now. So let’s get you Plexing in time for 
First off Logs
I doubt they still need them because a fix is being crafted, but this is how to zip your logs and drop them into Downloads in any case. Quit PMS then
cd ~/Downloads && zip -rj "Plex Media Server Logs_$(date '+%Y-%m-%d_%H-%M-%S')" ~/Library/Logs/"Plex Media Server"
Fixing your Mac
Basic Downgrading
Quit PMS. Drop the different version in /Applications and Replace.
Advanced Downgrading for you
If basic mode doesn’t work, and you probably tried it I’m guessing, then you need to move on to advanced downgrading. I posted How To Sign Out PMS on a MAC, Downgrade, and Reclaim where you can find the exact steps. Take care while you do it, and you’ll be up pretty soon.™
Notes
Always work closely with any Plex folk like BigWheel when they stop bye.
Again sorry to hear it’s frustrating. So post any questions, and good luck!
